Mechanism for unfolding accordion-like folded structural elements

ABSTRACT

Mechanism for unfolding series-connected, accordionlike folded structural elements, particularly for use in supporting large surface solar cells. The several sections to be folded and unfolded are connected by hinge structure including a torsion-bar tensioned when said parts are in a selected on of folded or unfolded conditions. In addition, force transmission means are arranged between panels which rotate in the same direction during movement in response to the urging of said tensioned torsion bars. These force transmission devices ensure that said arm sections will unfold (or fold) at predetermined ratios with respect to each other, regardless of the effectiveness of successive individual torsion bars and will further ensure predeterminable response by said arm sections, even if certain of said torsion bars are out of action. If desired, a power means can be applied to operate through said force transmission means for restoring the arm sections against the force of said torsion bars to said selected condition.

United States Patent [191 Maier et a1.

[54] MECHANISM FOR UNFOLDING ACCORDION-LIKE FOLDED STRUCTURAL ELEMENTS[75] Inventors: Horst Maier, Munich; Erich Arbeitlang, Ottobrunn; PeterKleber, Munich, all of Germany [73] Assignee: Messerschmidt-Bolkow-BlohmGesellschaft mit beschrankter Haftung, Munich, Germany [22] Filed: Apr.29, 1971 [21] Appl. No.: 138,451

[30] Foreign Application Priority Data 52/114,121, DIG. 4; 160/188, 193,213, 229, 206, l83;244/1 SS [56] References Cited UNITED STATES PATENTS3,525,483 8/1970 Van Alstyne ..160/l93 3,390,587 7/1968 Ratcliff, Jr..74/471 3,292,328 12/1966 Lewis et a1 ..52/D1G. 4 3,532,299 10/1970Williamson et a1 ..244/l SS 3,326,497 6/1967 Michelson ..244/l 3,627,58512/1971 Dollery et al.... 244/1 SS 3,477,662 11/1969 Anderson 160/1883,348,602 10/1967 Olsson ....160/188 3,217,785 11/1965 Hamilton..160/188 11] 3,733,758 1 51 May 22, 1973 3,121,977 2/1964 Bersudsky..52/D1G. 4

FOREIGN PATENTS OR APPLICATIONS 449,128 9/1927 Germany 1,050,499 2/1959Germany Primary Examiner-Frank L. Abbott Assistant Examiner-Leslie A.Braun Att0rney-Woodhams, Blanchard & Flynn [5 7] ABSTRACT Mechanism forunfolding series-connected, accordionlike folded structural elements,particularly for use in supporting large surface solar cells. Theseveral sections to be folded and unfolded are connected by hingestructure including a torsion-bar tensioned when said parts are in aselected on of folded or unfolded conditions. In addition, forcetransmission means are arranged between panels which rotate in the samedirection during movement in response to the urging of said tensionedtorsion bars. These force transmission devices ensure that said amsections will unfold (or fold) at predetermined ratios with respect toeach other, regardless of the effectiveness of successive individualtorsion bars and will further ensure predeterminable response by saidarm sections, even if certain of said torsion bars are out of action. Ifdesired, a power means can be applied to operate through said forcetransmission means for restoring the arm sections against the force ofsaid torsion bars to said selected condition.

11 Claims, 1 Drawing Figure MECHANISM FOR UNFOLDING ACCORDION-LIKEFOLDED STRUCTURAL ELEMENTS In the conception of large-surface solar-cellarms, particularly for satellites which consist of individual foldedpanels, there exists the problem of unfolding said panels easily andwith a minimum of special apparatus. Considering such criteria as highreliability and redundancy of the unfolding mechanisms, such desirableobjectives as a continuous unfolding operation, or the avoidance ofrestoring moments and the like acting onto the associated space vehicle,are difficult to attain. For example in a space vehicle with so-calledsolar-cell wings consisting of spiral-shaped foldable panels, whichspace vehicle is described in US. Pat. No. 3,326,497, each panel isconnected to the respective following panel through a motorized jointand, for the purpose of unfolding, the individual driving motors of alljoints are operated through'a sequence control. Such a system representsonly a partial solution to the described problem, partly because ofweight reasons and partly because of its complicated structure whichlatter increases its susceptibility to trouble.

The basic purpose of the invention is to produce a mechanism which issuitable for unfolding seriesconnected, accordionlike folded structuralelements, which mechanism is of simple construction and yet satisfiedthe above-mentioned criteria.

To attain this purpose the invention provides that drive means operatein connection with torsion-bar springs. Said latter are tensioned in thefolded position and are associated with structural elements, of whichadjacent ones are connected through torsion-bar spring bearings. Thedrive means consist of two disks each fixedly connected to theassociated structural element and a closed drive means, as a belt,connected to said disks for operation therewith. Each of said drivemeans connect two structural elements which during unfolding rotate inthe same direction of rotation.

By selecting torsion-bar springs as unfolding elements, if appropriate,in connection with radial step bearings and by means of drive meanswhich are in operative engagement with said springs, there is assured onthe one hand a movement control of the individual structural elementswhich movement control involves a minimum of frictional drag, and on theother hand the several drive means effect a continuous unfoldingoperation since they balance out different force components. Further, adefinite movement control is obtained by the drive means. Thus, bysuitably selecting each disk diameter any desired position of thestructural elements is possible after the unfolding. The unfoldedstructural elements can thereby, as far as this is necessary, be foldedagain by a central motor which increases the application possibilities.

To control the unfolding speed, speed-dependent damping elements, aspistons or the like, can also be provided to prevent an overstressing ofthe connections between the structural elements.

The invention will be explained more in detail hereinafter in connectionwith one exemplary embodiment, namely as applied to solar-cellarms,which is schematically illustrated in the drawing. Furtheradvantageous applications of the invention will be suggested thereby.

The drawing illustrates one-half of a circularly cylindrical centralmember 1 cut in longitudinal direction thereto, for example a satellite,and solar-cell arms 3 and 4 in partly unfolded position. Such solar-cellarms are arranged symetrically to the longitudinal axis 2 of the centralmember and are connected to said central.

member. Both of these arms are constructed identically and hence onlyone thereof is shown completely. Said arms have equal numbers of plane,rigid structural elements 5 and 6 and the structural elements 5' whichare directly associated with the central member 1 are constructed halfas long as the remaining structural elements 5 and 6.

Successively adjacent structural elements 5, 5' and 6 are hingedlyconnected and serve as carrier surfaces for the solar cells (notillustrated). Torsion-bar springs 8 are supported by radial bearings 7and are fixedly secured on the respectively associated structuralelement 5, .5 or 6 through axially fixed bearings 9. The same.connection is provided between the central member 1 and the two directlyfollowing structural elements 5'. The torsion-bar springs 8 aretensioned is the folded position of the arms 3 and 4 and hence will urgethe parts in unfolding direction. Thus, the structural elements 5, 5'and 6 can be unfolded safely and with a minimum of frictionalresistance. r

In order to assure a continuous unfolding operation which is symmetricto the unfolding direction, driving means 10, 11-, 12 and 13 are alsoprovided. Each of these consist of two circular disks 15, 15', 15" or 16and a closed force transmission means firmly connected therewith, forexample a belt or the like. The transmission means l0, l1, l2 and 13operatively engage one another in such a manner that by rotating anydesired structural element, for example one of the structural elements5' hingedly connected to the central member 1, such rotary movement istransmitted to the remaining structural elements 5, 5' and 6. This makespossible a continuous unfolding operation which takes place even ifseveral of the torsion-bar springs are out of action.

As illustrated in the drawings, this is accomplished by connectingthrough one of the transmission means 10, elements 5,5 which during anunfolding operation move in the same direction of rotation as thestructural element 5 hingedly connected to the central member 1. Thetransmission means 11 connects the two structural elements 6 which, incontrast to the elements 5', move in opposite directions of rotation.The transmission means 12 are associated at one end with the centralmember 1 and at the other end with one of the next adjacent structuralelements 6. The transmission means 13 having a direction reversaltransmission means, here a crossed belt, is provided as a connectorbetween the two arms 3 and 4. All pulleys 15, 15', and 15" are fixedlysecured on the respectively associated structural element 5, S and 6 andare mounted coaxially with the respective torsion-bar springs 8, whichsprings have their opposite ends fixedly connected to the adjacentstructural elements. For example, the torsion spring 8, between thecentral member 1 and the element 5' has its upper end fixedly connectedrelative to the central member 1 and its lower end fixedly connectedrelative to the panel 5'. In a similar manner, the torsion spring 8between the elements 5' and 6 has its upper end fixedly interconnectedto the element 6 and its lower end fixedly interconnected to the element5', and the torsion spring 8 between elements 5 and 6 has its upper endfixedly connected to the element 6 and its lower end fixedly connectedto the element 5. The disks 16 of the transmission means 12, which disksare associated with the central member 1, are in the same manner fixedlyconnected to the central member. Furthermore, all disks 15, 15', and 15"have the same diameter with the exception of the disks 16 secured to thecentral member 1. These disks 16 compared with the disks 15, 1S and 15"have relative diameters corresponding to the desired angular changebetween the structural elements 5, and 6. In this case the disks 16 aretwice the diameter of the disks 15, 15', and 15''. it is noted that alltransmission means 10, 11, 12 and 13 can also be arranged in a linealong one longitudinal edge which, however, results in an undesirableconstruction. For this reason the disks l5 and 15' of the drives or 13are fixedly secured through the respective radial bearings 7 on theassociated structural elements 5 and 5, respectfully and the remainingdisks and 16, are fixedly mounted through the respective torsion-barspring 8 on the associated structural element 6 and central member 1,respectfully.

Different components of force can be balanced out completely during theunfolding of the arms 3 and 4 with a series connection of transmissionmeans 10, 11, 12 and 13. Thus the system is almost independent ofexternally originating malfunctions. By choosing half structuralelements 5 on the central member 1, it is assured that the arms 3 and 4,connected with the central member 1, provide symetrical structurebefore, during and after the unfolding.

The two arms 3 and 4, the structural elements 5, 5' and 6 which are heldtogether in folded condition, if necessary, by means of straps, canafter releasing the holding means be moved synchronously under theeffect of the torsion-bar springs 8. Speed-dependent damping elements 14can be provided, if desired, to avoid thereby an unacceptably highstress on the torsion-bar spring bearings, namely at the end of theunfolding process. This is achieved, as illustrated in the drawing, byaxial pistons connected into the crossed transmission means of the drive13. It can also be provided that the structural elements 5, 5 and 6 canbe locked against one another the unfolded position, for example, bymagnets arranged on their transverse edges. They can then be combined toform one unit, namely independently from the unfolding mechanism. lncase that both arms 3 and 4 are to fold up again, this can be done by acentral motor which operates in connection with the drives 10, 11, 12and 13 and which must overcome the tension of the torsion-bar springsand holding force of the locking elements, for example magnets.

The reliability of the described mechanism can be increased by aredundancy in connecting further drives and torsion-bar springs. Thusthe mechanism is not only suitable for unfolding of solar-cell arms; itcan also be used in all other folding constructions, for example t Weclaim:

1. In an extendible structure having a plurality of structural membersmovably interconnected to each other, a hinge device coacting betweenthe adjacent ends of each pair of members for hingedly connecting saidmembers to each other in end-to-end relation, said plurality of membersbeing normally folded in an accordian-like manner, and transmissionmeans associated with said members for permitting uniform unfolding ofsaid plurality of members, comprising the improvement wherein saidtransmission means includes:

a plurality of pulley-like disks including first andsecond disksdisposed adjacent each of several adjacent hinge devices; means fixedlyinterconnecting said first pulley-like disk in nonrotatable relationshiprelative to one of the structural members associated with one hingedevice;

means fixedly mounting the second pulley-like disk in non rotatablerelationship relative to the other structural member associated withsaid one hinge device; and

a plurality of motion transmission devices associated with saidplurality of disks for effecting uniform unfolding movement of saidstructural members, each of said motion transmitting devices including asubstantially endless motion transmitting element extending between anddisposed in engagement with the first disk associated with one hingedevice and .the second disk associated with an adjacent hinge device.

2. An extendible structure according to claim 1, wherein said first andsecond disks are coaxially aligned with one another and are coaxiallyaligned with the hinge axis of the respective hinge device.

3. An extendible structure according to claim 2,

wherein each of said motion transmitting elements comprises a flexibleand endless cable-like member.

- 4. An extendible structure according to claim 3, wherein alternatecable-like members are disposed adjacent one longitudinal edge of saidplurality of members, and wherein the remaining cable-like members aredisposed adjacent the other longitudinal edge of said plurality ofmembers.

5. An extendible structure according to claim 1, wherein each of saidhinge devices includes an elongated torsion bar connected between eachadjacent pair of structural members for normally resiliently urging saidstructural members toward their respective unfolded positions, each saidtorsion bar having one thereof fixedly secured to one of the structuralmembers associated with each adjacent pair, and the other end of thetorsion bar being fixedly interconnected relative to the otherstructural member of each adjacent pair.

6. An extendible structure according to claim 5, wherein said first andsecond disks are associated with each torsion bar, said first disk beingnonrotatably secured to said one end of said torsion bar, and saidsecond disk being nonrotatably secured relative to the other end of saidtorsion bar.

7. An extendible structure according to claim 6, wherein each of saidmotion transmitting members comprises an endless and flexible cable-likemember extending between and engaged with a pair of disks associatedwith a pair of adjacent torsion bars.

8. Deployment mechanism for moving a multisectioned, accordian-likefolded structure of joinedtogether structural elements with the help ofdrawing means through disks arranged on the structural elements,particularly for use as a solar cell carrier for space travel purposes,comprising the improvement wherein the disks are alternatelynonrotatably connected to the adjacent structural elements, and whereinY the drawing means includes a plurality of closed and substantiallyendless drawing members extending between the engaging the adjacentpairs of disks for preventing slippage therebetween.

thereto.

1. In an extendible structure having a plurality of structural membersmovably interconnected to each other, a hinge device coacting betweenthe adjacent ends of each pair of members for hingedly connecting saidmembers to each other in end-to-end relation, said plurality of membersbeing normally folded in an accordian-like manner, and transmissionmeans associated with said members for permitting uniform unfolding ofsaid plurality of members, comprising the improvement wherein saidtransmission means includes: a plurality of pulley-like disks includingfirst and second disks disposed adjacent each of several adjacent hingedevices; means fixedly interconnecting said first pulley-like disk innonrotatable relationship relative to one of the structural membersassociated with one hinge device; means fixedly mounting the secondpulley-like disk in nonrotatable relationship relative to the otherstructural member associated with said one hinge device; and a pluralityof motion transmission devices associated with said plurality of disksfor effecting uniform unfolding movement of said structural members,each of said motion transmitting devices including a substantiallyendless motion transmitting element extending between and disposed inengagement with the first disk associated with one hinge device and thesecond disk associated with an adjacent hinge device.
 2. An extendiblestructure according to claim 1, wherein said first and second disks arecoaxially aligned with one another and are coaxially aligned with thehinge axis of the respective hinge device.
 3. An extendible structureaccording to claim 2, wherein each of said motion transmitting elementscomprises a flexible and endless cable-like member.
 4. An extendiblestructure according to claim 3, wherein alternate cable-like members aredisposed adjacent one longitudinal edge of said plurality of members,and wherein the remaining cable-like members are disposed adjacent theother longitudinal edge of said plurality of members.
 5. An extendiblestructure according to claim 1, wherein each of said hinge devicesincludes an elongated torsion bar connected between each adjacent pairof structural members for normally resiliently urging said structuralmembers toward their respective unfolded positions, each said torsionbar having one thereof fixedly secured to one of the structural membersassociated with each adjacent pair, and the other end of the torsion barbeing fixedly interconnected relative to the other structural member ofeach adjacent pair.
 6. An extendible structure according to claim 5,wherein said first and second disks are associated with each torsionbar, said first disk being nonrotatably secured to said one end of saidtorsion bar, and said second disk being nonrotatably secured relative tothe other end of said torsion bar.
 7. An extendible structure accordingto claim 6, wherein each of said motion transmitting members comprisesan endless and flexible cable-like member extending between and engagedwith a pair of disks associated with a pair of adjacent torsion bars. 8.Deployment mechanism for moving a multi-sectioned, accordian-like foldedstructure of joined-together structural elements with the help ofdrawing means through disks arranged on the structural elements,particularly for use as a solar cell carrier for space travel purposes,comprising the improvement wherein the disks aRe alternatelynonrotatably connected to the adjacent structural elements, and whereinthe drawing means includes a plurality of closed and substantiallyendless drawing members extending between the engaging the adjacentpairs of disks for preventing slippage therebetween.
 9. Deploymentmechanism according to claim 8, wherein some of the disks have differentdiameters.
 10. Deployment mechanism according to claim 8, wherein saidadjacent pairs of structural elements are hingedly connected inend-to-end relation by means of intermediate hinge rods.
 11. Deploymentmechanism according to claim 10, wherein each drawing member includes aspeed-dependently acting damping element connected thereto.